High purity aluminum alloy sputtering targets have been widely used in semiconductor manufacturing. To achieve desirable grain size and texture, aluminum alloy target blanks are typically fabricated by mechanical working and final recrystallization anneal. Since the recrystallization anneal decreases the mechanical strength of the aluminum alloys significantly, such fabricated aluminum alloy blanks are usually bonded to a much stronger commercial aluminum alloy backing plate. However, monolithic aluminum alloy targets sometimes are more desirable due to manufacturing simplicity, lack of debonding issues, and improved recyclibility. To reduce the target deflection during sputtering and improve mechanical reliability, monolithic aluminum alloy targets need to have adequate mechanical strength in addition to desirable metallographic attributes. Various fabrication techniques, such as equal channel angular extrusion (U.S. Pat. No. 7,017,382) and cryogenic rolling (U.S. Pat. No. 6,942,763) have been utilized to fabricate aluminum alloy targets with improved mechanical strength. The term “monolithic” refers to a single piece target unit devoid of any separate or attached backing plate structure.
The prior art approaches have certain limitations. Equal channel angular extrusion processes require complex and expensive dies, usually produce rectangular shaped plates, and thus are not cost-effective to make circular sputtering targets. Cryogenic rolling requires a cumbersome liquid nitrogen setup that may create health or safety issues. In addition, both processes are energy and labor intensive.